Sporadic WOT performance

[trobinson017]

Hi all, I thought I'd posted the problem before but I couldn't find it so reposting.

My Johnson 130 OceanPro outboard started having a problem with consistent running.
It idles okay and runs at low RPMs okay. But once I go to half throttle or WOT it starts
acting up. At half throttle it will level off at a lower RPM, then jump up to where it should be and then
back down. If I try to go WOT it won't even generate half the RPMs it should for about 10 seconds, but it will
suddenly jump to normal RPMs and the boat will speed up accordingly, then it drops back down to
about half power/RPMs. I'm running off of a 6 gallon external tank and have checked the intake there,
the fuel line, the fuel filter, etc. I took the carbs apart last month and everything looks/works fine.
A mechanic checked the fuel pump last fall for a different problem and that was okay then. There's no
water in the fuel. Fuel filter is clean. I just can't figure out what to check next.

Any ideas?

 

[viciousfishes]

Re: Sporadic WOT performance

Have you checked the magneto/coils? It might be that one of the coils is going bad when it heats up and causes you to lose a spark on one of the cylinders.

 

[nickzdad]

Re: Sporadic WOT performance

I am experiencing a similar kind of problem with my 1997 Evinrude 9.9 HP. I read a post on here where the gentleman eventually replaced the coil, sensor, and power pack to get rid of his 1997 9.9 HP Evinrude experiencing the same problems. Look at your ignition system and you might find your problem. I have ordered new ignition parts for my engine and hope to solve my problems that way.

 

[trobinson017]

Re: Sporadic WOT performance

UPDATE: I I pulled the #3 carb which in the past I found the float was sticking. Although it wasn't sticking this time I did notice that the float itself, when inverted, would drop below the rim of the bowl. So, my assumption is when in normal operation, the float would rise up above the bowl rim, possibly getting hung up on the bit of gasket that overhangs. I micro-adjusted it to be below the rim and now it at least gets to a planing speed consistently. Still not WOT speed but at least something positive has happened. I'm going to check the other carbs for similar issues.

FWIW, I talked to several local captains (fishing charters, tour boats, etc.) and they all believe my issue is fuel flow related. Combined, they gave me advice to pull each carb and make sure nothing is clogged or sticking and have a mechanic check the fuel pump. They don't believe it to be a magneto/coil issue.

 

[jonesg]

Re: Sporadic WOT performance

Try hitting the choke to bypass the carbs when its bogging down. If it picks up the carbs are faulty.

Try pumping the bulb to add fuel pressure, if it picks up rpm the pump is weak.

I wouldn't rul out ignition just on someones say so, do the proper spark test.
Then run it with a timing light on the wires to see if it drops spark under way.